The present invention relates generally to a bicycle gear shifting device, and more particularly to a mechanism for controlling the operation of the bicycle gear shifting device with ease and precision.
The conventional gear shifting mechanism on a bicycle is generally attained by a lever which is mounted on the handlebar and is connected with a gearshifting cable for actuating the derailleur. As the lever is triggered, the derailleur is actuated via the gearshifting cable to bring about the gear shifting operation. The cases in point include the U.S. Pat. No. 4,325,267 xe2x80x9cBICYCLE CONTROL LEVER DEVICE HAVING CONTROL LEVEL MOVEMENT CONFORMING TO A CYCLIST""S FINGERSxe2x80x9d, and the U.S. Pat. No. 4,840,081 xe2x80x9cSPEED-CHANGE OPERATING LEVER FOR A BICYCLExe2x80x9d. Such conventional gear shifting mechanisms as referred to above are not entirely effective in design in that the handlebar must be temporarily let go by the fingers of a bicyclist at the time when the bicyclist desires to activate the gear shifting mechanism. Such an operational maneuver as described above makes the bicyclist vulnerable to traffic accident.
The U.S. Pat. No. 5,197,927 xe2x80x9cBICYCLE CONTROL LEVER DEVICE HAVING CONTROL LEVERxe2x80x9d discloses an improvement on the bicycle gear shifting mechanism comprising a support seat which is mounted on the bicycle handlebar for fastening and locating the gearshifting cable. As the rotator is rotated, the gearshifting cable is wound by a camlike motion. The gear shifting operation is finally attained by a U-shaped elastic piece, which is retained in the arcuate grooves that are located in the support seat at various angles. Further improvements by the same inventor are disclosed in the U.S. Pat. Nos. 5,476,019 and 5,676,020. However, the gearshifting functions of these improvements on the mechanisms are seriously undermined by an additional friction force which is resulted from the complicated wirework of the mechanisms.
The U.S. Pat. No. 5,662,000 xe2x80x9cDETENT SPRING FOR ROTATABLE GRIP ACTUATING SYSTEMxe2x80x9d discloses a C-shaped elastic piece of a steel material, which is used in place of the U-shaped elastic piece of a plastic material to attain the gear shifting operation. However, the teeth of the arcuate grooves are vulnerable to wear, especially at the time of the return stroke of the support seat. As a result of the excessive force of the return stroke of the support seat, an unwanted gear shifting operation may be brought about at the time when the bicycle is subjected to a violent vibration on a bumpy road. In addition, the noise and the abnormal wear of the chain and the multisprocket are often resulted from the variation in the stroke even if the elastic piece is already retained by the teeth of the arcate grooves. This deficiency is due to the fact that the head of the gearshifting cable of the conventional gearshifting mechanism is fastened with the rotator.
It is the primary objective of the present invention to provide a mechanism for controlling the bicycle gearshifting device in such a manner that the elastic piece is located by the teeth of the arcate grooves with precision for an easy to-and-fro stroke operation, thereby resulting in reduction in wear of the component parts.
It is another objective of the present invention to provide a control mechanism of the bicycle gearshifting device with an independent cablelocating wheel set to enable the gearshifting cable to be installed and replaced easily.
The control mechanism of the present invention comprises a body set, an independent cable locating wheel set, and a rotator set.
The body set is provided at the center of the seat thereof with a hollow cylindrical portion, and a connection seat extending from the other peripheral edge of the seat. A gearshifting cable is put into the connection seat such that the gearshifting cable is connected at one end thereof with a derailleur. The seat is provided in the inner edge thereof with a plurality of locating portions. The independent cable locating wheel set is of a circular body, which is fitted over the hollow cylindrical portion of the body set and is provided in one side of the periphery thereof with a gearshifting cable head fastening seat, a curved block, and a curved elastomer of a thin platelike body and having an action portion which can be inserted into each of the locating portions of the body set.
The rotator set is provided with an arcuate protrusion extending from one end thereof such that the arcate protrusion is disposed in the control arcuate segment of the cable locating wheel set. The rotator set is provided at other end thereof with a hollow cylindrical portion which is engaged with the hollow cylindrical portion of the body set.
The foregoing objectives, features, functions, and advantages of the present invention will be more readily understood upon a thoughtful deliberation of the following detailed description of the present invention with reference to the accompanying drawings.